Obstetric complications and their relationship to other etiological risk factors in schizophrenia. A case-control study.

The history of obstetric complications was studied in 70 Research Diagnostic Criteria schizophrenic patients and 70 demographically matched controls from the same delivery series, using information prospectively recorded at birth. Schizophrenic patients were exposed to greater numbers of obstetric complications than their matched controls. Rates of obstetric complications were enhanced in patients born during the winter months (January-April) and in patients with no family history of psychosis in first- and second-degree biological relatives. Winter birth was associated with absence of family history of psychosis. Analyses by gender indicated that the relationship between obstetric complications and these other risk factors may be more relevant for male patients. The results suggest that the seasonal effect in schizophrenia may be due partially to seasonal variation in obstetric complications and that obstetric complications and winter birth may represent a distinctively separate etiological mechanism from that of inferred genetic risk for schizophrenia.